Plants annual or perennial; cespitose or rhizomatous. Culms 5–160 cm, erect or geniculate at the base, glabrous; basal branching extravaginal. Sheaths closed almost to the top; ligules membranous; blades flat to folded, adaxial surfaces with prominent midribs. Inflorescences terminal, racemes, rarely panicles. Spikelets laterally compressed, with 5–20(30) florets, upper florets reduced; disarticulation above the glumes and beneath the florets. Glumes unequal to subequal, shorter than the adjacent lemmas, membranous to subhyaline, margins scarious; lower glumes 1-veined; upper glumes 1–3-veined; rachilla internodes in some species swollen and glandular basally, the glandular portion turning whitish when dry; calluses rounded, glabrous; lemmas thick, herbaceous to membranous, 7(9)-veined, veins parallel, margins scarious, apices scarious, entire or emarginate, midvein sometimes extended into an awn, awns straight; paleas subequal to the lemmas, 2-veined, keeled over each vein, keels winged, with 1 or 2 awns or a flat triangular appendage; lodicules 2, completely fused; anthers 3, opening by pores; ovaries glabrous. x = 8, 9, 10. Name from the Greek, pleura, ‘side’, and pogon, ‘beard’, a reference to the awns on the sides of the palea in some species.
Pleuropogon is a genus of five hydrophilous species, one circumboreal in the arctic, the other four restricted to the Pacific coast of North America, extending from southern British Columbia to central California. The Pacific coast species are sometimes treated as a separate genus, Lophochlaena Nees, but are here regarded as constituting a subgenus of Pleuropogon.
The flat, triangular paleal appendages differ from bristly or flattened awns in being wider at the base, and smooth rather than scabrous.
SELECTED REFERENCES But, P.P.H. 1977. Systematics of Pleuropogon R. Br. (Poaceae). Ph.D. dissertation, University of California, Berkeley, California, U.S.A. 229 pp.; But, P.P.H., J. Kagan, V. Crosby, and J.S. Shelly. 1985. Rediscovery and reproductive biology of Pleuropogon oregonus (Poaceae). Madroño 32:189–190.